(1) Field of the Invention
The invention relates to a binder composition comprising water glass and an organic hydrocolloid material, in particular psyllium. It relates further to path material comprising such a binder composition and to the use of the binder composition for binding an aggregate. The invention relates further to a method for providing a traffic area or parts of a traffic area, wherein the binder composition is used.
(2) Description of Related Art
Various materials for areas (or parts thereof) which are subjected to pedestrian or vehicular traffic are known. The most widely used materials are unbound materials, such as, for example, gravel, sand, stone chips or crushed sand mixtures. The strength and durability of the path areas or joint fillings produced with these construction materials are low and the susceptibility to erosion is high, weed infestation of these areas and joints increases with the length of their use. These construction materials can be both permeable to water and impermeable to water.
A second group of known construction materials for traffic areas is bound materials. By means of, for example, cement, asphalt or polymers (plastics), lime, etc. or mixtures thereof, materials such as, for example, gravel, sand, stone chips and crushed sand mixtures (aggregates) can be permanently bound.
These construction materials are distinguished negatively by possible cracks and fissures after freeze-thaw cycles and settling, joint-filling products in particular are affected thereby. The sides of the stones delimiting the joints break away from the jointing material. However, these bound construction materials are more durable than the unbound materials. The bound materials are, however, rigid and monolithic, plants (weeds) establish themselves in the cracks that form. These materials are in most cases impermeable to water and seal surfaces.
A third group are the semi-bound construction materials. The semi-bound construction materials are more resistant to erosion than are the unbound materials and are at the same time flexible, resilient, so that, for example, a movement of paving stones relative to one another or settling of the base course (substrate) can be accommodated.
In the known prior art, aggregates are mixed either only with psyllium or with the addition of mineral additives. The disadvantages of this application are known:
Psyllium on its own tends to disintegrate and/or to be washed out by rainwater, plant growth is not reduced. Although the addition of mineral additives increases the erosion resistance as compared with the sole use of psyllium, the strength of the traffic areas is not improved. The additives that bring about erosion resistance often leave a white or grey film on the stone areas filled with the jointing material, the area is soiled. The use is not user-friendly.
Examples of the third group of construction materials are disclosed in WO 2006/029539 A1. A binder mixture of psyllium, calcium hydroxide and sodium carbonate is described therein as a binder composition, and its use as a component of path material is also disclosed. The compositions described in this document exhibit in particular film formation when used as jointing material, and the erosion resistance is in need of improvement.